Welcome to this lecture on the spinal cord.
Our first slide depicts a lesion of the spinal cord.
This lesion is involving the dorsal columns/medial lemniscal system.
The lesion at this level within the spinal cord is affecting the first order neurons as they ascend
and this lesion then is ipsilateral
and as a result to this lesion being on the ipsilateral side of the pathway,
there will be an ipsilateral loss of function below this level of the lesion.
The loss of function would involve the loss of fine touch,
loss of pressure and vibration senses,
as well as conscious proprioception
as these are the normal functions that are conveyed by this ascending pathway.
Here, you’re looking at a cross-section through the spinal cord.
And the lesion is depicted over here in the shaded light green area.
And so if we identify the lesion and the accompanying clinical features,
the lesion that’s a hemisection of the spinal cord as you see here
is referred to as Brown-Séquard Syndrome.
is gonna involve various aspects of the spinal cord,
the dorsal columns would be involved
in through here.
So again, this will be ipsilateral loss of fine structure,
two-point discrimination, vibration, pressure,
and conscious proprioception
at and below that particular level of the lesion.
The spinothalamic tracts are also involved here
and in this case, there will be a contralateral loss of pain and temperature
1-2 segments below the lesion,
and the reason that the loss of pain and temperature is 1-2 segments below the lesion
is due to Lissauer’s tract.
Lissauer’s tract, when the neurons, or at this level are ascending a couple of levels,
and so this is involving those levels that are below this particular level in the spinal cord.
Please note specifically that at level of the lesion, there is complete ipsilateral loss of all sensations.
Lastly, the corticospinal tracts are involved.
and at this particular level, there will be an ipsilateral paresis
at and below the lesion.
Here, we’re looking at a continuation of Brown-Séquard Syndrome.
In addition, to what we saw in the previous slide,
descending hypothalamics will be lesioned.
And so we lose the descending hypothalamic output.
And at this lesion is above spinal cord level T1.
The loss of sympathetics will result in ipsilateral Horner’s Syndrome.
So, miosis, anhidrosis, and ptosis
would be the triad of symptoms associated classically with Horner’s Syndrome.
Lower motor neurons would be involved here.
They would be damaged in the dorsal grey horn area
and as a result there will be flaccid paralysis at the level of the lesion.
And as it’s shown here, with paralysis, loss of muscle tone,
and just a general state of hypotonia.
Here, we’re looking at again a cross-section of the spinal cord
but this is a different lesion, or have a different set of clinical features.
Here, the lesion is, in this area of the cord, the posterior part.
So it’s involving the dorsal columns.
This particular lesion is referred to as Tabes Dorsalis.
And this disease is characterized by a slow degeneration,
demyelination of nerves
found primarily in these dorsal columns.
So, you have the fasciculus gracilis and the fasciculus cuneatus
ascending through this area of the spinal cord.
What are the accompanying clinical features of tabes dorsalis?
Individuals that have this lesion
complain of intense pain.
They complain of disturbed sensation.
and then usual high step gait.
There gait it is unsteady
and they will exhibit a positive Romberg’s sign,
which is demonstrated by a loss of balance when the patient has their eyes closed.
And this will be due to a loss of proprioception.
Due to disruption of proprioception, patients also exhibit sensory ataxia.
Sensory ataxia is characterized by an unsteady, stomping gait.
This is exaggerated when the eyes are closed.